The present invention relates generally to an automatic circuit back-up system for a data communication network. More specifically, the invention relates to an automatic circuit back-up system to be employed in a data communication system including a private communication circuit for data communication and a back-up communication circuit for providing a back-up for the private communication circuit.
Conventionally, such automatic circuit back-up system performs switching a data channel from the private communication circuit to the back-up communication circuit for maintaining data communication when failure of the private communication circuit or a data circuit-terminating equipment (DCE) is detected. In the automatic circuit back-up system, states of the private communication circuit and the data circuit-terminating equipment are constantly monitored. However, back-up circuit condition due to circuit failure caused by breakage of cable or equipment condition, such as failure of the automatic circuit back-up system in a distant office, can be recognized from data back-up operation due to detection of failure in the private communication circuit or the data circuit-terminating equipment, or from connect from the distant office in response to a message for changing or reading of the setting the automatic circuit back-up system in the distant office.
Therefore, if circuit failure in the back-up communication circuit or failure of the automatic circuit back-up system in the distant office is caused upon detection of failure of the private communication circuit or the data circuit-terminating equipment, switching of the data channel from the private communication circuit to the back-up communication circuit cannot be performed. As a result, the reliability of the overall communication system is degraded.